1. Field of the Invention
The invention relates generally to filtration, and more particularly to a coupler for joining filtration elements.
2. Description of Related Art
Filtration membranes are used for the removal of unwanted particles or organisms from various types of fluids. Typical uses for filtration membranes include treatment and purification of drinking water, cleaning and treatment of wastewater for disposal or re-use, sludge de-watering, desalination, and clarification of juices, wines, and beverages. Filtration membranes include spiral-wound, hollow fiber, and tubular membranes. Most often, the spiral wound filtration membrane is enclosed in a hard outer wrap to form a filtration element. One or more spiral wound filtration elements are placed within a housing to form a filtration assembly. Fluid to be treated is forced under pressure into the inlet end of the filtration assembly and through the filtration membrane. Material is rejected by the filtration media while permeate passes through the media and is removed for use or further processing.
In one type of filtration assembly known in the art, two or more filtration elements, each comprising spiral-wound filtration membranes secured between two anti-telescoping end pieces, are placed end-to-end within a filtration assembly housing. The leading end, on the upstream side, of each element includes a circumferential brine seal around its outer perimeter that seals against the interior surface of the filtration cartridge housing. The brine seal also serves to position the element within the housing. Additional filtration elements may be placed end-to-end within the housing to provide a larger assembly.
However, the configuration of the known art imposes significant restrictions on filtration capability. For instance, the friction fit of the protruding brine seal on the outer perimeter of large diameter filtration elements makes it difficult to insert or pull the element into the housing, or to remove it when necessary for inspection or replacement. Since a larger diameter brine seal proportionally increases the contact area and correspondingly the friction, the larger the diameter of the element the greater the resistance to insertion of it into a housing. This drawback is compounded when attempting to insert or remove multiple filtration elements all having brine seals joined end to end into or from the housing of a filtration assembly. Increasing the force used to insert or remove the filtration elements may result in damage to the filtration elements.
Another factor in designing systems employing spiral-wound filtration membranes is the inherent tendency of the membrane to “telescope” under the system pressures present in the filtration process. When the system is designed for fluid to enter the end area of a spiral-wound membrane element, the end area is open to allow maximum fluid flow. Increasing the diameter of the filtration membrane proportionally increases the cross-sectional area of the membrane exposed to system pressure. Under pressure, the center portion of a spiral-wound membrane may be moved longitudinally, commonly referred to as “telescoping”. The telescoping problem also increases with increasing diameters.
Additionally, the known art relies partially on the friction of the brine seal between the filtration element and the housing to position adjoining filtration elements within the housing, as well as to provide a seal between the elements and the housing. Thus, if a brine seal is damaged during the assembly process, not only is the sealing function compromised, the filtration element may be able to move relative to an adjoining element and the integrity of the separation process may be compromised. Large “wiper type” brine seals or large O-ring brine seals are subject to the deficiencies discussed above. Also, chevron or v-shaped brine seals when placed on multiple elements joined end to end require insertion at one end of the housing and withdrawal at the opposite end. This means substantial floor space at both ends of the housing must be left clear.
The prior art also contemplates the use of a circumferential band which overlaps two adjoining filtration elements to further hold the elements in place as well as to retain a seal which may be placed between the ends of two filtration elements. This construction does not lock the elements together so they can be pulled through a housing, and it does not provide a positive compression seal between adjoining elements.
Thus there exists a need in the art for a filtration element that may be easily and securely interlocked to an adjoining element, and that also allows single or multiple coupled elements to be easily inserted into, and removed from, a filtration assembly housing utilizing a single brine seal.